Shooting subsonic ammunition is significantly quieter than shooting supersonic ammunition. Simple fluid dynamics tells us that if a projectile travels at a velocity below the speed of sound, the sonic crack normally heard with supersonic projectiles will not be present. When used in combination with a sound suppressor, subsonic ammunition significantly reduces a firearm's sound signature to hearing-safe levels. Subsonic ammunition has become increasingly popular with today's civilian, law enforcement and military shooters for the following uses: